Sofa



FIG. 1 is a perspective view of a sofa showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a right side view thereof, the opposite side being a mirror image of the side shown.

The rear view is not part of the claimed design. 

The ornamental design for a sofa, as shown and described. 